In recent years, display devices to be incorporated in smartphones or tablets have been required to have a higher resolution and a higher aperture ratio. If the resolution is made higher, and as a result a pixel size is reduced, the ratio of a signal line and a light-shielding layer to a pixel area is increased, and the aperture ratio is thus reduced. Furthermore, since it is necessary to restrict occurrence of color mixing, it is difficult to reduce the ratio of the signal line and the light-shielding layer to the pixel area.
As an example of a technique for ensuring a sufficient aperture ratio while achieving a higher resolution, it is known that a pixel is made up of two subpixels, i.e., a red subpixel and a green subpixel or a blue subpixel and a white subpixel.